This invention is in the field of wireless communications, and is more specifically directed to adaptive bidirectional communications over multiple frequency bands.
Wireless communications, of many types, have gained increasing popularity in recent years. The mobile wireless (or “cellular”) telephone has become ubiquitous around the world, including in those locations in which landline telephone facilities are not available. Mobile telephony has recently begun to communicate video and digital data, in addition to voice, especially as the so-called 2.5G and 3G services are deployed. Wireless modems, for communicating computer data over a wide area network, using mobile wireless telephone channels and techniques, have also been available for some time. Wireless data communications in the computer network context have also become popular. Wireless local area network (LAN) technology, such as that operating according to the well-known IEEE 802.11 standard, has become especially popular in a wide range of installations, ranging from home networks to commercial connectivity such as in airports, coffee shops, and hotels. Short-range wireless data communication according to the “Bluetooth” technology is now becoming popular, permitting computer peripherals to communicate with a personal computer or workstation within the same room.
Mobile wireless telephony is generally carried out over so-called “licensed” frequencies. These licensed frequencies refer to frequency bands in the overall spectrum that are regulated by a government entity, for example the Federal Communications Commission in the United States. Examples of licensed frequency bands include those around 800 MHz for conventional mobile cellular telephony, and those around 1.9 GHz for mobile personal communication services (PCS). Typically, mobile telephone communications are carried out over paired (uplink and downlink) frequencies within the licensed band. The licensing of frequencies permits those parties that have paid for the license rights to have exclusive use of a particular licensed frequency band within a geographical region. This licensing minimizes the likelihood of interfering communications, permitting the exclusive licensee to control traffic in that vicinity and to have recourse against unauthorized transmitters in those bands. These license rights enable the license holders, such as wireless telephone service providers, to invest in mobile wireless communication infrastructure, such as base stations, switching facilities, and the like.
Because of the license fees associated with licensed transmission and the investment in infrastructure, the licensed entities in turn generally charge their customers for use of their infrastructure and services. Typically, these charges are based on usage time, regardless of the data or signal volume used in the communications. Accordingly, licensed entities such as wireless telephone service providers have an interest in increasing the capacity of their licensed frequencies, especially considering that most licensed bands are quite narrow, thus limiting the data volume that can be carried. If the capacity of a licensed band can be increased, the revenue available to the licensed entity for a given infrastructure investment will also increase.
Unlicensed bands are also available in the radio spectrum. As evident from the term “unlicensed”, radio transmission of signals in the unlicensed bands involves no license fees, so long as the transmitter complies with certain regulations regarding the use of these allocated unlicensed frequencies. An example of an unlicensed band is the so-called instrumentation, scientific, and medical (ISM) band around 2.4 MHz; other unlicensed bands also exist, including a band at around 900 MHz within the otherwise licensed PCS band, and a band at around 5.2 GHz. As a result, many types of devices now available transmit radio signals in the unlicensed bands, including landline telephones with wireless handsets, wireless local area network (LAN) adapters and access points, Bluetooth computer peripherals, and the like. Current allocations of the unlicensed bands permit a large amount of bandwidth with no license fee, resulting in the deployment of many systems that provide high data rates (on the order of Mbps) and large spectral bandwidths (on the order of MHz). However, a great deal of interference from other unlicensed band users must often be tolerated in these bands.
In recent years, not only has the coverage area of wireless telephony greatly improved, but also wireless LAN access has become widely deployed. It is believed that both of these trends of improving coverage and access will continue. In addition, many indoor locations such as office buildings and conference facilities have implemented both wireless LAN functionality and improved licensed wireless telephone coverage. As a result, many locations are now within range of both wireless LAN access and licensed wireless telephony.
Another trend in the industry is the implementation of additional media sources and applications into mobile handheld electronic devices. For example, personal digital assistants (PDAs) models now include wireless Internet access, including such functions as web browsing, sending and receiving emails, and the like, generally via wireless communication over licensed bands. New generations of mobile wireless telephones (e.g., the so-called “2.5G” and “3G” mobile wireless telephone standards) are also attaining additional functionality, including still and motion video capability, web browsing, and email functionality. So-called “Blackberry” mobile wireless email devices are now also commonplace. Indeed, the line between PDA and mobile telephone devices is becoming somewhat blurred.
By way of further background, dual-mode mobile wireless telephone handsets are known in the art. One type of dual-mode telephone handset provides the capability of either digital or analog transmission, depending upon the availability of digital wireless telephone coverage; in these telephones, the handset transmits and receives digitally when in digital coverage, and switches to analog communication only when digital coverage is not available (considering the higher power dissipation and poorer performance of analog transmission). Another type of dual-mode mobile telephone handset is capable of transmitting using a selected one of multiple modulation techniques, such as GSM, CDMA, or TDMA. The selection may be made upon activation of the mobile handset in connection with a particular service.